1. Technical Field of the Invention
This invention relates to a current detection switch for detecting a current flowing into an electric circuit installed in a vehicle, a ship, an airplane, etc., and outputting the detection result and apparatus using the current detection switch.
2. Related Art
In recent years, vehicles each with a battery as a power source, such as electric automobiles and hybrid cars, have been becoming pervasive, and it has become important to manage charge and discharge of the battery. As a current detector used to manage charge and discharge of the battery, for example, a detector using a magnetoelectric device to detect a current flowing into an electric circuit is known. However, in this kind of current detector, the magnetoelectric device also reacts with a disturbance magnetic flux and thus precise current detection is difficult to execute; this is a problem.
To solve such a problem, for example, JP-A-63-253264 (JP-B-8-3499) discloses xe2x80x9ccurrent detector.xe2x80x9d The current detector comprises a conductor 51 for allowing a measured current 52 to flow, magnetoelectric devices 54 and 55 for converting a magnetic field occurring in the surroundings of the conductor 51 when the measured current 52 flows into the conductor 51 into electricity in the areas opposed to the surroundings of the conductor 51, and a combining section 56 for combining conversion outputs of the magnetoelectric devices 54 and 55, as shown in FIG. 9.
In the current detector, the magnetoelectric devices 54 and 55 have the same characteristic and receive magnetic fields of the same magnitude, different in direction with respect to a magnetic loop 53 occurring when the measured current 52 flows into the conductor 51. Thus, outputs from the magnetoelectric devices 54 and 55 are in opposite phase and if the outputs are differentially combined in the combining section 56, output of the combining section 56 becomes approximately twice output of the single magnetoelectric device. Consequently, the sensitivity of the current detector can be approximately doubled. on the other hand, when an external magnetic field 57 affects the whole current detector, the outputs from the magnetoelectric devices 54 and 55 are in phase with respect to the external magnetic field 57. Therefore, if the outputs are differentially combined in the combining section 56, output signals based on of the external magnetic field 57 are canceled out. Consequently, the effect of the disturbance magnetic field is excluded.
However, with the current detector disclosed in JP-A-63-253264 (JP-B-8-3499), if the disturbance magnetic fluxes input to the two magnetoelectric devices 54 and 55 do not have the same magnitude, the disturbance magnetic fluxes are not canceled out. A situation in which the disturbance magnetic fluxes input to the two magnetoelectric devices 54 and 55 differ in magnitude can occur depending on the positional relationship between the current detector and the magnetic flux generation source and if the situation occurs, the current detector cannot detect a current normally.
It is therefore an object of the invention to provide a current detection switch capable of detecting a current flowing into a measured conductor and outputting a detection signal without being affected by a disturbance magnetic flux and apparatus using the current detection switch.
To achieve the above problem, according to a first aspect of the invention, there is provided a current detection switch comprising:
a measured conductor into which a measured current flows;
a plurality of magnetoelectric devices placed sandwiching the measured conductor so as to have magneto-sensitive faces on sides to which a magnetic flux generated by the measured current is input, each of the magnetoelectric devices for outputting a magnetoelectric signal when the magnetic flux exceeds a predetermined value; and
a computation section for outputting a logical multiplication of the magnetoelectric signals from the plurality of magnetoelectric devices as a detection signal.
According to the first aspect of the invention, when no disturbance magnetic flux exists, every magnetoelectric device outputs a magnetoelectric signal when the magnetic flux generated by the measured current flowing into the measured conductor exceeds the predetermined value, whereby the computation section outputs a detection signal. In contrast, when disturbance magnetic flux exists, each magnetoelectric device outputs a magnetoelectric signal when the arithmetic sum of the magnetic flux generated by the measured current flowing into the measured conductor and the disturbance magnetic flux (the sum considering the direction of the disturbance magnetic flux) exceeds the predetermined value.
That is, the magnetoelectric device with the disturbance magnetic flux added to the magnetic flux generated by the measured current flowing into the measured conductor outputs a magnetoelectric signal if the current value is smaller than the predetermined threshold value, but the magnetoelectric device with the magnetic flux canceled out by the disturbance magnetic flux does not output a magnetoelectric signal unless the current value is larger than the predetermined threshold value. Consequently, the computation section outputs a detection signal when a larger current than the predetermined threshold value flows. In other words, when the measured current is equal to or less than a certain value, the current detection switch does not react with the disturbance magnetic flux and thus can detect the current flowing into the measured conductor without being affected by the disturbance magnetic flux.
According to a second aspect of the invention, in the current detection switch of the first aspect, the computation section outputs the logical multiplication of the magnetoelectric signals from the plurality of magnetoelectric devices and an abnormal signal from an outside when a vehicle is abnormal as the detection signal.
According to the second aspect of the invention, the computation section outputs the logical multiplication of the magnetoelectric signals from the plurality of magnetoelectric devices and an abnormal signal from an outside when a vehicle is abnormal as the detection signal, so that a detector such as a current detection switch, for example, when a circuit is dead-shorted because of a shock at the accident time and an abnormal current occurs can be configured.
According to a third aspect of the invention, there is provided a circuit breaking apparatus comprising:
a current detection switch including,
a measured conductor into which a measured current flows,
a plurality of magnetoelectric devices placed sandwiching the measured conductor so as to have magneto-sensitive faces on sides to which a magnetic flux generated by the measured current flowing into the measured conductor is input, each of the magnetoelectric devices for outputting a magnetoelectric signal when the magnetic flux exceeds a predetermined value, and
a computation section for outputting a logical multiplication of the magnetoelectric signals from the plurality of magnetoelectric devices as a detection signal.
a circuit breaker for shutting off the current flowing into the measured conductor; and
a break drive section for causing the circuit breaker to shut off the current flowing into the measured conductor in response to the detection signal from the current detection switch.
According to the third aspect of the invention, the circuit breaking apparatus is configured using a current detection switch for detecting a current flowing into a measured conductor and outputting a detection signal without being affected by disturbance magnetic flux, and thus can shut off a circuit reliably regardless of the presence or absence of disturbance magnetic flux.
According to a fourth aspect of the invention, there is provided a load failure detecting apparatus comprising:
a current detection switch including,
a measured conductor into which a measured current flows, the measured conductor being connecting a power supply to a load,
a plurality of magnetoelectric devices placed sandwiching the measured conductor so as to have magneto-sensitive faces on sides to which a magnetic flux generated by the measured current flowing into the measured conductor is input, each of the magnetoelectric devices for outputting a magnetoelectric signal when the magnetic flux exceeds a predetermined value, and
a computation section for outputting a logical multiplication of the magnetoelectric signals from the plurality of magnetoelectric devices as a detection signal;
a load switch for supplying a current from the power supply to the load; and
a warning device for generating a warning when the detection signal is not output from the current detection switch with the load switch turned on.
According to the fourth aspect of the invention, the load failure sensing apparatus is configured using a current detection switch for detecting a current flowing into a measured conductor and outputting a detection signal without being affected by disturbance magnetic flux and thus can notify a load failure and a broken conductor regardless of the presence or absence of disturbance magnetic flux.